N1 4X4

 When It’s Not Music To Your Ears

When It’s Not Music To Your Ears

Most Toyota 4×4 owners believe that the sound of their vehicle is part of its charm, but today we talk about that CLUNK sound that varies between a bad Elvis impersonation, your first pan flute lesson, and some ADHD little drummer boy.

A 4-wheel drive vehicle has many drivetrain components that can cause a clunking sound when they get worn, loose, or damaged. These would typically be the CV Joint, ball-joints & U-Joints, the transfer case, the front differential, tie-rod ends, or suspension bushes.

Sometimes, when you engage 4-wheel drive on the fly above a certain speed, your transmission could produce a clunking sound, caused by the gears inside the transmission case as they engage to lock the front and rear driveshafts. This is not necessarily something to worry about.

It may happen that you hear a noise from the front of your vehicle when turning, due to a CV joint failure. This is the most common cause of clunking sounds on a 4-wheel drive. Remember that CV joints are Constant-Velocity joints that allow the vehicle’s driveshaft to convey power to the wheel at an adaptable angle, at a constant rotating speed, without more friction or play. If you want to find out whether a CV joint is a culprit, you must go through a process of elimination, first to identify which side the noise comes from. Make a few figure eights and circles and if you hear the sound when you turn sharp right that means that the right CV has a problem, and vice versa. Sometimes the sound will only be loud when you accelerate into a corner – the clunking would be faster as the wheel rotation picks up.

Other things to take note of is the condition of the rubber bush cover of the CV joint – if torn the grease meant to lubricate the ball bearings inside could have leaked out, causing heat build-up, friction and damage.

The many small components in the drive train system of a 4-wheel drive (one with independent front suspension in particular) are designed to keep the vehicle stable, to help with steering, and to allow for movement of the suspension control arms. Sometimes the universal joint (U-joint) at the ends of the drive shafts could be creating a clunking noise when accelerating in 4-wheel drive mode (even though in 2H it may be quiet).  When the U-joint rubber caps are worn out, dirt could damage the needle bearings inside the u-joint, and the effect would be a loud clunking sound when the vehicle accelerates.

The worst-case scenario would be when the front differential has failed, due to low diff oil levels, drivetrain binding or simply because of off-road abuse. When you remove the differential and you find metal filings inside the housing it means that (a) the ring gear teeth broke off (b) the pinion gear teeth broke off (3) the spider gear has broken teeth or (4) other carrier damage has occurred. You might be lucky and the damage is minor, but the internal diff gearing will need complete replacement eventually.

When the differential rubber mounts on your vehicle are loose, excessive play and vibration could occur under load when 4-wheel drive is engaged and accelerating.

Metal-on-metal noises could be caused by a loose axle mount, most likely due to the rubber bush that has perished and cracked. Sometimes clunking noises can also be caused by the sway-bar link, control arm Bolts, and shock mountings.

We all shirk when we hear that familiar grind or bang when a newbie shifts into 4WD while the rear wheels are rotating.  One should understand that engaging 4-wheel drive while driving essentially locks the front and rear driveshafts together while one is stationary and the other is spinning at a few thousand RPMs! When the splines mesh without a glitch there should be no bang or grinding noise, meaning that the front wheels were rotating at a speed close enough to that of the rear wheels. Sometimes, the splines interlock and the whole lot starts turning together, but this could still make the internal gears inside the transfer case lose a few teeth. In the instance that the splines fail to interlock, you will hear a grinding noise.

A clunking noise could also be caused by the driveshaft binding when your 4-wheel drive locks up when turning. When this happens, your vehicle will under-steer heavily, its gears will get jammed and steering will become dreadfully difficult or will shudder. This means that, as the front drive shaft tries to slow down the front wheels it battles against the rotation causing the pronounced under-steer effect. You should avoid engaging 4WD on a high traction surface at all costs. The longer you drive in that mode, you risk serious damage to your drive-train components and you will find it increasingly difficult to remove it from 4WD mode and switch back to 2WD mode.

So…if you hear something cacophonic in your 4×4’s orchestral manoeuvres, bring your vehicle to us for repairs or a service: https://n14x4.co.za/rmi-workshop/

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